Nothing herein contained shall require any change
in the plans, construction or designated use of a building for which
a building permit has been heretofore issued or plans for which are
on file with the Construction Official at the time of the passage
of this chapter and a permit for the erection of which is issued within
three months of the passage of this chapter and the construction of
which, in either case, shall have been diligently prosecuted within
a year of the date of such permit, and the ground-story framework
of which, including the second tier of beams, shall be completed within
such year, and which entire building shall have been completed according
to such plans as filed within two years from the date of the passage
of this chapter.
Nothing in this chapter shall prevent the restoration
of a wall declared unsafe by the Construction Official or by a Board
of Survey.